Issue 46

Y. Yanya, Frattura ed Integrità Strutturale, 46 (2018) 343-351; DOI: 10.3221/IGF-ESIS.46.31 346 collected using a measuring cylinder. The time (t) and the amount of effluent water (Q) were recorded. Each test specimen was measured thrice. The maximum and minimum values were removed from the test results, and the median was taken as the permeability coefficient of the test specimens. The calculation formula is: i Ql k Aht  (2) where K i stands f or the permeability coefficient at the i-th measurement (unit: cm/s), Q stands for the amount of water passing through the test specimens in t seconds (unit: cm 3 ), l stands for the height of the test specimens (unit: cm), A stands for the cross section area of the test specimens (unit: cm 2 ), h stands for the difference of water level (unit: cm), and t stands for the measurement time (unit: s). Figure 1. Test device Compressive strength and splitting tensile strength The compressive and splitting tensile strength of the recycled pervious concrete were tested using YAW6506 electro- hydraulic servo compression testing machine according to Standard for Test Method of Mechanical Properties on Ordinary Concrete (GB /T 50081-2002). T EST RESULTS AND ANALYSIS The analysis results of the physical properties of coarse aggregate oarse aggregate acts as a skeleton in concrete, which determines the properties of concrete mixture and the mechanical and endurance properties after hardening. The main properties of the natural and recycled aggregate were detected using relevant regulations in this study, and the results are shown in Tab. 3. Physical property indexes Water content/ % 10-min water absorption/% 24-h water absorption% Apparent density/ (kg/m 3 ) Stacking density/ (kg/m 3 ) Porosity /% Silt content/ % Crush index/% Recycled aggregate 2.9 5.0 5.6 2606 1262 51.62 0.25 35.07 Natural aggregate 0.2 0.4 0.5 2728 1553 45.33 1.4 15.56 Table 3: The physical properties of the natural aggregate and recycled aggregate. Tab. 3 demonstrates that the water content of the recycled aggregate was 14 times that of the natural aggregate, the 24-h water absorption of the former was about 12 times that of the natural aggregate, and the 10-min water absorption of the recycled aggregate was 90 % that of recycled aggregate in saturated water absorption state. It was because that the hardened mortar on the surface of the recycled aggregate was so porous that the water absorbability was strong. The C